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Wednesday, September 5, 2018

An
analysis of the chemical signals sent out by rice plants under attack by the
brown planthopper could help in natural control of this insect pest.

Researchers in Indonesia have deciphered the chemical cues used by rice to
attract a parasitoid that helps fight off the plant’s predator. The researchers
created a system to imitate these cues, which could help investigate similar
interactions in other crops and possible sources of non-toxic pest control.Rice is a staple food, relied upon by half the global
population. The brown planthopper is one of rice’s most destructive pests,
causing damage by wounding the stem of the plants to lay the eggs for the next
attack and by transmitting viruses that attack the plant.Researchers from Universitas Negeri Malang and the Indonesian
Sweetener and Fibre Crops Research Institute led by Dr. Surjani Wonorahardjo, Chemistry Department, Faculty of Mathematics and Science, Universitas Negeri Malang, Indonesia, wanted to see if they could target
the brown planthopper without using pesticides known to harm the environment.
To do this, they investigated the so-called ‘tritrophic interaction’ between
rice, the brown planthopper and the parasitoids that prey on the brown
planthopper’s eggs.They extracted samples from rice infected by the brown
planthopper and analysed their chemical makeup. They then compared this to what
they found in samples taken from healthy rice, identifying the chemical
differences between healthy and infested rice.They created a porous material from rice husk and soaked
different pieces in chemicals extracted from either healthy or infected rice.
In laboratory tests, the parasites were more attracted to the material infused
with the infested sample. They also attached infused materials to posts and
placed them outside in a rice field. Again, they found more parasitoids on the
infected sample, but the researchers observed that the effect wore off over
five days, so the samples effectively had an expiration date.The results, published in the Pertanika Journal of Science and Technology, could guide further trials to see if applying the chemical
cue could actually reduce the pest’s destruction of rice paddies; and if so, to
what degree. The use of analytical chemistry offers insights into the
mechanisms underlying these interactions and detect small changes taking place
in great detail.

They note that their technique exploring the interaction
between plant, pest and the pest’s own predator on a chemical level requires
further refinement, but could eventually be applied to other agricultural crops
and potentially reduce the use of harmful pesticides.Isaac Oyimah/GEE